1. Field of the Invention
The present invention relates to a steam trap which is connected to steam-operated equipment or steam tubes to automatically discharge condensate.
2. Description of the Related Art
A conventional float type steam trap is shown in FIGS. 13 and 14. A float type steam trap 50 shown in FIG. 13 is constructed so that a cylindrical inner valve 53 is fixed to a lever 52, one end of which is fixed and the other end of which is supported so as to be turnable, and the inner valve 53 moves up and down following the up-and-down movement of a float 51.
Also, a float type steam trap 60 shown in FIG. 14 is constructed so that a spherical inner valve 63 is fixed to a lower end portion of a lever 62, one end of which is fixed to a float 61 and the other end of which is supported so as to be turnable, and the inner valve 63 is opened and closed along with the turning action of the lever 62.
In the float type steam trap shown in FIGS. 13 and 14, taking the buoyancy of float as F, the distance from the center of float to the turning center position of lever as L1, the distance from the turning center position of lever to the installation position of inner valve as L2, the cross-sectional area of an outflow port as A, and the difference in condensate pressure between the inlet side and the outlet side of outflow port as ΔP, the condition for opening the valve is expressed by the following equation.F×L1>A×ΔP×L2  Equation (1)
In order to open the valve in the conventional float type steam trap, in Eq. (1), F or L1 has only to be increased, or A, ΔP or L2 has only to be decreased. However, an increase in F or L1 presents a problem of increased size of the entire device.
Also, a decrease in A leads to decreased discharging capability, and a decrease in L2 leads to decreased discharging capability of condensate because a sufficient lift of inner valve cannot be provided. Further, a decrease in ΔP restricts the service condition, and hence presents a problem of loss of versatility.
Also, the valve seat system that determines the valve closing performance of the conventional float type steam trap is a surface contact system of up-and-down motion for the type shown in FIG. 13, and a line contact system of spherical surface for the type shown in FIG. 14. Therefore, the closing performance and durability are incomplete, and thus there arises a problem of steam leakage etc.
To solve these problems, in the conventional float type steam trap with high discharging capability, the size of the entire device is large, and the usable ΔP is small. Also, the device in which the size thereof is small and the usable ΔP is large has low discharging capability. Therefore, there is a tendency for increased number of device types and for increased-size of device to meet wide-range specifications.
Thus, the requirements imposed on the float type steam trap are as follows:
1) The entire device, which has conventionally been large in size, is downsized, the discharging capability is increased, and the service pressure range is widened.
2) The closing performance and durability are improved, unnecessary consumption of steam is eliminated, and economical operation is realized.
3) The occurrence of water hammer caused by sudden closure of inner valve is prevented.
4) In a device having high condensate discharging capability, continuous discharge can be effected even when the inflow amount of condensate is small.
5) The float is prevented from moving violently and being damaged due to sudden inflow of condensate or disturbance such as vibrations during transportation of device.
In order to solve the conventional problems as described above, the inventors have developed a float type steam trap having a valve element, which slides with respect to a valve seat in association with the up-and-down movement of float so as to be able to open and close the valve seat, provided on a float (see Japanese Patent Laid-Open No. 2002-195492).